1. Field of the Invention
The invention relates to a stent/graft deployment catheter, particularly for repairing defects in arteries and other lumens within the body. More particularly, the invention relates to a stent/graft deployment catheter, having a positive stent attachment mechanism on its distal end, for delivering a stent/graft in situ for repairing defective body lumens, and particularly abdominal aortic aneurysms.
2. Description of the Prior Art
An abdominal aortic aneurysm (AAA) is a sac caused by an abnormal dilatation of the wall of the aorta as it passes through the abdomen. The aorta is the main artery of the body, supplying blood to all organs and parts of the body except the lungs. It arises from the left ventricle of the heart, passes upward, bends over and passes down through the thorax and through the abdomen, and finally divides into the iliac arteries which supply blood to the pelvis and lower extremities
The AAA ordinarily occurs in the portion of the aorta below the kidneys. When left untreated, the aneurysm will eventually cause the sac to rupture with ensuing fatal hemorrhaging in a very short time. The repair of abdominal aortic aneurysms has typically required major abdominal surgery in which the diseased and aneurysmal segment of the aorta is bridged with a prosthetic device, such as a synthetic graft.
As with all major surgeries, there are many disadvantages to the above mentioned surgical technique, the foremost of which is the high mortality and morbidity rate associated with surgical intervention of this magnitude. Other disadvantages of conventional surgical repair include the extensive recovery period associated with such surgery; difficulties in suturing the graft to the aorta; the unsuitability of the surgery for many patients, particularly older patients exhibiting comorbid conditions; and the problems associated with performing the surgical procedure on an emergency basis after the aneurysm has already ruptured.
In view of the above mentioned disadvantages of conventional surgical repair techniques, techniques have been developed for repairing AAAs by intraluminally delivering an aortic graft to the aneurysm site through the use of a catheter based delivery system, and securing the graft within the aorta using an expandable stent. Since the first documented clinical application of this technique was reported by Parodi et al. in the Annals of Vascular Surgery, Volume 5, pages 491-499 (1991), the technique has gained more widespread recognition and is being used more commonly. As vascular surgeons have become more experienced with this endovascular technique, however, certain problems have been encountered. One major problem involves deployment of the stent/graft. Substantial friction between the outer surface of the graft material and the inner surface of the delivery sheath of the deployment catheter makes it sometimes difficult to deploy the stent/graft device precisely in the right location while not exerting significant forces which may damage the stent/graft device. The traditional expandable stent/graft is radially compressed before insertion into the delivery sheath. The more the stent/graft device can be compressed the smaller the introducer sheath and the catheter can be made. Therefore, a highly compressible stent/graft is desired. One problem with radially compressing a given stent/graft to its maximum extent is that once the compressed stent/graft is inserted into the delivery sheath of the catheter, friction between the outer surface of the graft and the inner surface of the delivery sheath, caused by the restoring force of the compressed stent/graft, makes it very difficult to push the stent/graft out of the delivery sheath of the catheter, and therefore, makes it difficult to accurately deploy the stent/graft without damaging it. In light of this design limitation, the total cross sectional area of a traditional expandable stent/graft in its compressed deployment state is generally designed 10% to 30% less than the area of the corresponding delivery sheath in order to limit friction between the graft and the delivery sheath and to ensure that the stent/graft is not damaged upon deployment.